Early notions of digitizing the activities at what might be thought of as an "electronic blackboard" date at least to the mid-1960s, at which time emphasis was placed on the communication of graphical data, specifically handwriting and sketches, from one location to another. U.S. Pat. No. 3,706,850 discloses a system related to such activity.
At about the same time, interest was strong afoot in digitizing the activity on a tabletop - - - for example for the entry of line drawings into a computer. Systems involving this interest are collectively known as graphic tablets, and U.S. Pat. No. 3,838,212 is an early example of development matters in this area.
By the mid-1980s, a third kind of a product group developed to address the need for creating a local hard copy of material written and sketched onto a dry-erase, so-called whiteboard. This generic group of systems, known collectively as electronic copyboards (ECBs), relates fundamentally to stand-alone devices that have much in common with well known reducing photocopiers.
Each of these devices attempts, in its own right so-to-speak, to provide the user with a natural communication metaphor - - - with familiar writing tools. In the cases of the electronic blackboard and the electronic copyboard, the metaphor is a wall-mounted surface meant for mass viewing, with marking or writing accomplished by colored markers, and erasing occurring by wiping with an eraser. In the case of the graphic tablet, the metaphor is a desktop slate and stylus meant for individual use.
Those skilled in the art recognize that both electronic blackboards and electronic copyboards typically require special surfaces and are relatively expensive. Further, they do not readily support the use of color presentations, and the typical electronic copyboard cannot communicate real-time transitional information - - - i.e. it must batch-transmit (like a facsimile) an entire sheet, or page, of information at a time.
Other systems and approaches generally in this line of technical art are illustrated, for example, in U.S. Pat. Nos. 4,558,313, 4,777,329 and 5,023,408. The '313 patent focuses on an indicator-to-data processing interface which employs a light source and a background reflector as constituents in a system to monitor occlusion of light occurring from the positioning and movement of a manually moved indicator over a surface. The '329 patent, which is based upon on my own prior line of development in this field, addresses attention to a graphic input system which employs ultrasound to monitor the position of a mobile element over a surface. The '408 patent describes an electronic blackboard including a sensing tablet which senses the position of a "writing tool" that includes a tuned circuit having a predetermined resonant frequency.
All of these various approaches in the prior art in this area offer, in their own respective ways, operational advantages in certain applications, but nevertheless also have some common, as well as differentiated, deficiencies which are correctively addressed by the system of the present invention. For example, prior art systems of the type outlined above are relatively complicated and costly (as mentioned). They are not necessarily readily retrofittable, for example, to a wide variety of writing-surface structures which are already in hundreds of thousands of users' possessions. Further, prior art systems are not particularly adapted to yield information about the condition of a writing stylus or an eraser (write-effective component) much beyond its position or station over a writing surface. Many systems, as already indicated, cannot communicate changing, real-time positioning of such a component. Nor are known prior art systems adapted to handle more sophisticated informational issues, such as (1) differentiated writing-line widths which may result from differentiated angulation of a writing stylus, or (2) parallax under similar circumstances, or (3) the width of an eraser swath under circumstances where an eraser's configuration is such that it has different effective erasure-widths from different angular points of view.
Accordingly, and in the setting just described, a general object of the present invention is to provide a novel graphic data-acquisition system which offers not only the various features and advantages made available by prior art, generically-related systems, but which also addresses effectively the various performance, cost, simplicity and sophistication, etc., issues just briefly mentioned.
Proposed by the present invention, with these considerations in mind, is a code-based electromagnetic-field-responsive, and preferably optically (or near optically) responsive, one-to-one, graphic data-acquisition system which employs active transceiver structure (a pair or more preferably), including a scanning light-beam source and a light-reflection (or light-retroreflection) monitoring structure (1) to create a zone of scanned or swept radiation extending closely over a defined writing-surface area, and (2) to monitor reflections (or retroreflections) of such radiation from such an area, all in cooperation with a passive write-effective component, such as a writing stylus (pen, marker) or eraser, which is equipped with code structure, such as a bar code structure, that reflects (retroreflects), or otherwise interacts responsively to, radiation created (by scanning) over the writing-surface area. As mentioned, the system of the invention preferably operates in the optical, or near-optical, portion of the electromagnetic spectrum. Thus, in the preferred embodiment of the invention described herein, two transceiver structures are employed at spaced stations, with each such structure including a light source in the form of a laser operating generally in the optical, or perhaps more precisely in the near-optical, portion of the electromagnetic spectrum, and specifically, at a preferred wavelength of 780-nanometers. The system is referred to as a one-to-one system since communication takes place directly between a transceiver structure and a write-effective component moved over the writing-surface area.
By employing passive, radiation-responsive code structure on a component that moves over a writing surface to create or remove images, the system achieves remarkable simplicity. Further, by utilizing a code structure associated with such a component, a great deal of information, quite beyond simply that relating to the position of the component relative to the writing-surface area, can be acquired. For example, one can distinguish immediately whether the component is a writing implement or an erasing implement, can determine the nature or character of written line width or eraser swath, can detect, for example, specific color in the instance of a colored writing instrument being used, and also with respect to a writing instrument, can provide data regarding inclination relative to the writing-surface area, and hence any related changes in written line width, and in parallax. A data stream generated from the monitoring structure which forms part of each transceiver structure in the system can be used in a variety of ways, such as for example, to feed information into the memory of a digital computer, and/or to feed information for transmission, for example over a voice-grade telephone line, to remote stations for "live" presentation of "writing activity" occurring on the writing-surface area in the system, etc.
A modified form of the system utilizes a "nonmarking" stylus and a "nonerasing" eraser whose travel paths over the associated writing-surface area are followed to effect back-projection illumination or de-illumination of a conventional translucent screen which forms the writing-surface area.
The system of the invention employs conventional triangulation, derived from the use of at least two, spaced transceiver-structure stations, to track the position and motion of a writer or eraser, and the components of the system are readily retrofittable, at relatively low cost, to a wide variety of otherwise conventional writing-surface structures, such as so-called dry-erase whiteboards.
Various other features and advantages which are attained and offered by the invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.